Oedematous Skin Disease of Egyptian Buffaloes

Oedematous Skin Disease (OSD) is a significant and endemic bacterial infection affecting Egyptian buffaloes, leading to substantial economic losses due to reduced milk yield, hide damage, and occasional mortality. The disease is caused by Corynebacterium pseudotuberculosis (serotype II), with its primary virulence factor being the exotoxin Phospholipase D (PLD). This toxin induces severe local inflammation, edema, and systemic toxemia.Epidemiologically, OSD exhibits a distinct seasonal pattern, with outbreaks predominantly occurring during the hot and humid summer months (April-August). The insect Hippobosca equina (the horse fly) is identified as a key mechanical vector in disease transmission. Morbidity rates in buffalo herds are notably high, reported at 26.1% to 30%, while mortality rates are lower, ranging from 4% to 4.5%. Case fatality rates can be significant, reaching up to 13.3%, particularly in severe forms of the disease.Clinically, the disease manifests primarily in two forms: a cutaneous form and a more severe mixed (cutaneous-renal) form. The cutaneous form is characterized by hot, painful, edematous swellings, typically on the limbs, which may progress to ulceration, crust formation, and lameness. Systemic signs include fever, anorexia, and depression. The mixed form involves renal damage, evidenced by hemoglobinuria ("coffee-colored" urine), and is often fatal due to shock and organ failure.Diagnosis is confirmed through bacteriological isolation of C. pseudotuberculosis, Gram staining revealing characteristic rods, and serological tests like Agar Gel Immunodiffusion (AGID) and ELISA that detect antibodies against the PLD toxin.Treatment strategies show varying efficacy. A medicinal approach combining antibiotics (e.g., Penicillin-Streptomycin) and anti-inflammatory drugs has a success rate of approximately 66.6%. In contrast, surgical intervention for abscessated lesions is highly effective, with a 100% success rate. However, treatment often fails in advanced or mixed-form cases due to the intracellular nature of the bacterium and the profound systemic effects of the toxin.In conclusion, OSD remains a major challenge for the Egyptian buffalo industry. Effective control measures should focus on developing immunization strategies against C. pseudotuberculosis and its toxins, coupled with rigorous control of the Hippobosca equina vector population